IPC for app icons drag events over the Bubble Bar

Added an IPC call to inform the Bubble Bar in the launcher process
of drag events from the shell.

Bug: 388894910
Flag: com.android.wm.shell.enable_bubble_bar
Test: Manual. Check that events from the shell process successfully
reach the launcher process.

Change-Id: I01615911ce7e4250138aedaa5823f639b9163ff0